The present invention relates directly to lift systems on agricultural implements and, more specifically, to a depth control actuation system for such implements.
Agricultural implements with hydraulically actuated depth or lift systems often include depth control systems such as shown in commonly assigned U.S. Pat. Nos. 5,427,184 and 5,988,293. A typical system may include a valve which is activated to stop vertical movement of the frame as the implement is lowered to a selected working position.
Many hydraulically controlled agricultural implements utilize a single point depth control system wherein implement depth is monitored and adjusted at a single location on the implement. Typically, a plunger bracket assembly is slidably mounted on an actuator tube operably connected to the implement rockshaft. A plunger on the assembly contacts a poppet valve to stop fluid flow from the hydraulic lift cylinders at a preselected depth. To adjust depth, a set screw on the bracket assembly is loosened, and the bracket assembly is slid along the tube. The screw is tightened to secure the assembly at the desired location along the tube. Normally the amount of depth adjustment is small. When the set screw is unthreaded, the bracket is loosened from the tube and slides on the tube, often to a wrong location. The bracket has to be manually moved, and the amount of adjustment has to be determined visually. When the set screw is tightened, the bracket often changes location. Several trials may be required to achieve the desired position. Therefore, depth adjustment is often imprecise, difficult to repeat, and time consuming.
In another type of depth control, which is the subject of commonly assigned U.S. Pat. No. 5,427,184, a long crank is provided to adjust a linkage adjacent the depth control cylinder. Although such a device has the advantage of directly monitoring cylinder extension and retraction, the valve and linkage components are more complicated, expensive and difficult to access, and are subject to damage by crops and soil passing through the machine. A further type of control is shown in commonly assigned U.S. Pat. No. 5,988,293. Although these types of devices have alleviated some of the problems associated with depth control structures, most require complicated and expensive linkages, particularly if the depth adjustment is conveniently located for the operator. Wear and hysteresis limit the ability of such structures to provide accurate and repeatable depth control functions.
It is therefore an object of the invention to provide an improved depth control system for an implement. It is a further object to provide such a system which overcomes most or all of the aforementioned problems. It is still another object to provide such a system which is particularly useful with single point depth control structures.
It is another object of the invention to provide an improved depth control system for an implement having reduced hysteresis and improved repeatability compared to at least most previously available systems. It is a further object to provide such a system which is less complicated, easier and less expensive to manufacture, and easier to access than most systems.
A depth control system includes a valve and actuator mounted directly to the pivotal connection areas of a hydraulic cylinder that controls height. Cylinder motion therefore directly controls valve actuation independently of complicated linkages to reduce the size and cost of the system and substantially overcome hysteresis problems. These and other objects, features and advantages of the invention will become apparent from the description below in view of the drawings.